Reference Number: 4
Sourdough lactic acid bacteria were preliminarily screened for proteolytic activity by using a digest of albumin and globulin polypeptides as a substrate. Based on their hydrolysis profile patterns, Lactobacillus alimentarius 15M, Lactobacillus brevis 14G, Lactobacillus sanfranciscensis 7A, and Lactobacillus hilgardii 51B were selected and used in sourdough fermentation.
A fractionated method of protein extraction and subsequent two-dimensional electrophoresis were used to estimate proteolysis in sourdoughs. Compared to a chemically acidified (pH 4.4) dough, 37 to 42 polypeptides, distributed over a wide range of pIs and molecular masses, were hydrolyzed by L. alimentarius 15M, L. brevis 14G, and L. sanfranciscensis 7A.
Albumin, globulin, and gliadin fractions were hydrolyzed, while glutenins were not degraded. The concentrations of free amino acids, especially proline and glutamic and aspartic acids, also increased in sourdoughs. Compared to the chemically acidified dough, proteolysis by lactobacilli positively influenced the softening of the dough during fermentation, as determined by rheological analyses. Enzyme preparations of the selected lactobacilli which contained proteinase or peptidase enzymes showed hydrolysis of the 31-43 fragment of A-gliadin, a toxic peptide for celiac patients.
SIGNIFICANCE OF THIS STUDY
Celiac disease is one of the most frequent genetically based diseases, occurring in 1 out of every 130 to 300 persons in the European population. The exact mechanism of the damaging effect in celiac patients is still unknown, however, all the major gliadin proteins from some cereals (e.g., wheat, barley, and rye) have been shown to be the trigger in initiating the immune response and the disease process. The above findings encourages the use of lactic acid bacteria for breaking down gliadin-derived peptides, which are involved in celiac disease. Toxic peptides derived from the proteolytic (breakdown of proteins) digestion of the proteins (prolamins-mainly gliadins) of some cereals (e.g., wheat, barley, and rye) adversely affect the intestinal mucosa of celiac patients. This study is regarded one of the first studies to demonstrate the hydrolysis of albumin, globulin, and especially gliadin fractions by sourdough lactic acid bacteria. Although there have not been any large clinical studies showing the effectiveness of these breads on celiac patients, this paper provides valuable insights for further advancements in the potential of using sourdough type breads with low gliadin toxic peptides as a suitable option for individuals with celiacs or wheat intolerances.